Keep having Misfire issue.....

Z

zizaspeed

Member
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2004 RX8
Alright so I picked my p5 up about 3 weeks ago with a cylinder 2 misfire (p0302). To keep the story short, this being my second protege I kind of knew the run down on what to do. First thing was I bought plugs, got some used coil packs and wires which also came with injectors. Changed all those parts. Still had the code but it changed to p0300. Cleaned EGR valve and IAC I think it is called (on top of throttle body), code changed back to p0302. Each time I did something to the car I either disconnected battery for awhile or cleared code with scanner. Today got brand new coil packs from autozone and denso wires and put those guys in. And a code came back with 30 minutes. In between all of this I also put a new intake in since my factory one was cracked. I don't know what code came up today because I have yet to check it, I plan on doing so tomorrow. But if there is anything I'm not doing or anything you guys would advise me to do that would be great. I also have been running injector cleaner in gas tank every time I pump, have not seafoamed and am not sure If I really want to. Thanks in advance.
 
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so just checked the code, and its back to random misfire, p0300. So i'm going to see if it comes up again as a random misfire and if it does then switch the coil packs around and see if it switches.
 
Yeah I bought new ones from autozone yesterday cause the used were still giving me issues. But with the new ones in I still had a code come up....
 
Yeah I bought new ones from autozone yesterday cause the used were still giving me issues. But with the new ones in I still had a code come up....
 
do you actually feel the car misfire? Try cleaning the MAF with MAF sensor cleaner, cleaning the EGR valve, and/or seafoaming the car. Does it happen while idling or while driving? Check for vac leaks
 
The code only appears when car is started or sitting at an idle, not while driving....hella annoying. I cleaned EGR valve and IAC plunger on top of throttle body.
 
do you have any other codes beside that one? Definitely seafoam the car(through brake booster and gas tank) and try the MAF cleaner.
 
yeah, i just used some electrical cleaner, really hope the stupid light doesnt come back.....really can't think of anything else it coulde be
 
So I got another random misfire code, this time on freeway. I read the mans Canadian egr post and it said that a faulty egr can cause the ecu to send a misfire code. So I unplugged egr and drive a few miles and no code so far.
 
Yeah, I figured I would just try it out and see. On that same post about canadian egr, there were multiple people who had just unplugged it and had no issues. I figure I could give it a shot and see if I have the same luck. I'm still going to buy a new egr though.
 
A code did come up again, man this is so annoying. The car seems to run perfectly fine, sometimes it will hesitate but that's when the engine is cold. I just hate seein that light on...I'm hoping its the EGR
 
I seafoamed the car last wednesday, lots of white smoke. The code came back. Just had trouble starting it yesterday cause I think it misfired as i was starting it, the code came back after I started it....
 
So it's been awhile since I updated this but, since that time everything I have changed includes; coilpacks, used injectors, plugs, wires, intake (factory was cracked), clean IAC valve, replaced EGR with revised canadian one.

I still get the random misfire everyone once in awhile maybe 1 every 2 weeks, and it goes away on its own within like 2 days(I think like 3 driving cycles).

At this point I don't really know what else to do, but have read on here that misfire can lead to pre cat failure? Another thing I have noticed is my mpg is between 21-24, I'm not sure if that is normal or not? Any suggestions on what to do next would be great, I'm thinkin about replacing the 02 sensors possibly but thats pricey and don't want to waste money if I don't have to.
 
What kind of plugs did you put in? You might consider pulling them and checking the gap. I read somewhere on here that the factory gap is .045". If the gap's too small (or too big, also), you could have a small, randomly-reoccurring misfire.

And if the plugs you put in have any connection to Bosch, pitch them and get something else. Hell, basic Champions are better than Bosch plugs. (Me, I'm partial to NGK V-power or Denso.) I'm also very anti-Platinum plugs, but that's a personal preference.
 
Change your pcv valve if you haven't already. You may also have a bad purge control solenoid. It will cause poor gas mileage. Dunno about the misfires but it's possible. The purge control solenoid is normally closed. i.e. if the car is off and you take a vacuum line off of it you should not be able to blow threw it.
 
I put the NGK stock replacement in, either v or g I can't remember. I assumed they came pre-gapped so didn't both regapping. I believe I already changed pcv valve just because. Where is this purge control solenoid at? Thanks.
 
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